The invention relates generally to a foodware article having a tarnish-resistant coating, and more particularly to a foodware article having a thermally stable, tarnish-resistant, ceramic coating on the outer heat source-contacting surface, and to a method of making such foodware articles.
Ceramic coatings, such as TiN, ZrCN, and TiCN, have been used in a variety of applications, including faucets, door hardware, signs, various architectural uses, and other industries because of their decorative appearance and anti-tarnish properties. These applications do not involve direct contact with a heat source, such as gas flame or electric heating element.
Ceramic coatings have been used as non-stick coatings or for stick resistance on the food-contacting surface of cookware, for example, U.S. Pat. Nos. 5,447,803, 6,197,438, and 6,360,423. However, these coatings were not used on the heat source-contacting surface of the cookware. Moreover, U.S. Pat. No. 6,197,438 states that various ceramic coatings, including TiN, TiCN, ZrN, CrN, and AlTiN, have poor flame color stability. It does not describe what tests were run or the conditions under which they were performed.
Cookware can be made from a variety of materials, including cast iron, copper, aluminum, and steel. Each type of cookware has advantages and disadvantages.
Seasoned cast iron cookware has a tough, abrasion resistant surface. However, cast iron is subject to rusting, and it must be cleaned carefully to avoid damage to the cookware surface. In addition, acidic foods can cause leaching of the iron from the surface, which can lead to health problems in some cases.
Copper cookware has excellent heat transfer properties. However, it is easily scratched because it is much softer than other cookware materials, such as cast iron or stainless steel. Copper also oxidizes readily, which leads to tarnishing. Copper can be polished to remove the tarnish, but it requires substantial effort to maintain the surface finish.
Aluminum cookware has excellent heat transfer properties. However, aluminum also tarnishes easily. It cannot be polished, but it must be scoured on a regular basis because stovetop burners and food particles can easily discolor it.
Stainless steel cookware is widely used. It is known for its strength and durability. Stainless steel is relatively easy to clean, and it holds its shine better than copper. However, stainless steel is a poor heat conductor. In order to overcome its poor heat conducting properties, aluminum or copper disks are often added to the bottom of stainless steel pots or pans. In many cases, the bottom of the foodware is made of copper or is copper-plated. Alternatively, aluminum or copper layers are clad with stainless steel to produce a multilayer product. However, if a stainless steel pan has exposed copper, the copper has to be polished to keep it shiny.
Although many people like the appearance of copper cookware, the amount of time and effort required to maintain the finish prevents many people from using it. Therefore, there is a need for an easy-to-maintain, tarnish-resistant coating for foodware.